Steel nails often rust when exposed to the elements. To prevent this, corrosion-resistant finishes are typically utilized to protect the nails. One such method of incorporating corrosion protection is to manufacture nails from steel wire that is pre-plated with zinc to provide galvanic protection.
One problem with such method relates to the protection of the head or head portion of the nail. More specifically, the head portion of the nail is typically formed by deforming the steel wire. When the head portion of the nail is formed, the zinc plating on the steel wire is also deformed and often results in uneven distribution of zinc across the entire nail head portion. While the resulting zinc layer still provides certain amounts of galvanic corrosion protection, especially during the harsh conditions of exposure to moisture, the head portion of the nail thus often experiences at least some cosmetic corrosion over time at one or more of the locations on the head portion where the zinc is thinner or non-existent. This corrosion typically occurs in relatively milder dry conditions, where galvanic protection is only provided to areas covered with zinc. Improving the uniformity and continuity of the zinc layer on the nail head portion is highly desirable to improve corrosion resistance in all conditions.
Another problem relates to conventional methods used to entirely coat steel nails with heavy levels of zinc that require immersion of the nails in molten zinc at temperatures of 800 degrees to 1100 degrees Fahrenheit (which is sometimes referred to as “hot-dip galvanizing”). Such hot-dip galvanizing has various processing issues. First, hot-dip galvanizing is a batch process that can introduce variation from batch to batch. Second, adding a batch process in the middle of manufacturing a product can add to operational complexity, inefficiency, and expense. This process is also especially cumbersome when nails will be subsequently processed to be aligned and collated for use in automatic nail-driving tools. For instance, untreated nails are removed from the manufacturing line, hot-dip galvanized in a batch, and then the treated nails are reintroduced into the manufacturing line. The inventory of untreated nails and treated nails must be managed carefully not to cause delays in the manufacturing process. For example, if the inventory of treated nails is exhausted before the next batch of untreated nails finishes the hot-dip galvanizing batch process, the manufacturing process will be delayed. Third, handling the nails during hot-dip galvanizing typically heats the nails to a level that can cause the heated nails to become weakened and bend. Bent nails increase waste in the post-galvanizing processes and in many instances cannot be sold and need to be discarded. This increases waste and also increases cost. Fourth, the quality of the galvanized layer must be inspected for each batch that is processed. Variations from batch to batch can result in subsequent manufacturing difficulties and inconsistent quality of corrosion protection that is provided.
A known improved method versus this conventional hot-dip galvanizing process is to manufacture hot-dip galvanized wire and then cut and form the nails from that wire. There are advantages to this method. First, the wire galvanizing processes result in substantially smoother and more uniform zinc plating layers than the batch-galvanized nails. Nails made from such wire are substantially more uniform in dimension, and improvements in manufacturing efficiency and reductions in scrap are realized when nails are aligned and collated for use in automatic nail-driving tools. Second, galvanization of wire is typically a continuous process, which enables much larger quantities of steel to be galvanized in a batch than pre-formed nails. This greatly reduces the amount of inspection that must be performed to ensure that the zinc plating on the nails meets manufacturing and corrosion protection requirements.
However, a disadvantage to the manufacturing of nails from galvanized wire is that coverage of the zinc plating may not extend across the entirety of the formed nail head or head section. When the galvanized wire is cut and the head portion is stamped, the zinc plating on or around the head portion is disrupted. The zinc tends to be malleable and can flow in the same manner as the underlying steel to form the head; however, continuity is compromised and areas with little or no zinc can result on the top of the nail head surface. Practically, relatively enough corrosion resistance is maintained across and around the nail head surfaces due to the overall presence of zinc. Typical harsh environmental conditions that necessitate corrosion resistance in application include rain and condensation. Wet environmental factors enable the zinc to provide broad galvanic protection across the entire nail head surface when it is wet, almost regardless of the uniformity or continuity of the zinc layer. While drier conditions are not considered to be as corrosive to metals, drier environmental conditions do not permit zinc to have as much “throwing power”, which enables exposed steel on the nail heads to oxidize locally and create superficial rust. Cosmetically, this is undesirable. The known solution to remedy this cosmetic issue is to apply an anti-corrosion paint on the nail head surface. This solution is not satisfactory because it provides a mixed barrier or mixed galvanic method of protection that is not the same as the rest of the nail.
Accordingly, there is a need to provide a new method and apparatus for applying a more consistent corrosion-resistant coating to fasteners (such as nails) that solve these problems. There is a need to provide new fasteners (such as nails) that solve these problems.